function sayName(person: {name: string}): void {
  console.log('Hello! ' + person.name);
}

let bill = {
  name: 'Bill',
  gender: 'boy'
}

sayName(bill);


interface People {
  name: string;
  age: number;
  gender: string;
}

function sayHello(person: People): void {
  console.log('Hello, ' + person.name);
}

let lucy = {
  name: 'Lucy',
  age: 21,
  gender: 'girl'
}

sayHello(lucy);